Increases in the concentration of greenhouse gases in Earth's atmosphere lead to warming of the Earth's global climate. This is because greenhouse gases, such as CO2 (carbon dioxide), limit the passage of ultraviolet radiation through the Earth's atmosphere.

Question

Figure 1 shows levels of atmospheric CO2 over the past 400,000 years. As Figure 1 shows, the concentration of atmospheric CO2 has risen to a higher level than at any other time in the last 400,000 years. Figure 2 shows levels of atmospheric CO2 concentration since 1750. Both figures support the hypothesis that the rate of increase of CO2 concentration in the atmosphere has been rising dramatically.

Many scientists have connected this dramatic increase in atmospheric CO2 to human activities—mainly the burning of fossil fuels and mass deforestation—that transfer stored carbon from the Earth's surface to the atmosphere. Although CO2 levels have been higher at other points in Earth's history, the high rate of increase demonstrated over the past two centuries has raised questions about how the global climate will respond to an increased greenhouse effect.

Answer 1

The increase in atmospheric CO2 concentration has significant implications for Earth's climate system. As you noted, greenhouse gases, including CO2, absorb and emit infrared radiation, trapping heat in the atmosphere. This greenhouse effect is critical for maintaining the Earth's temperature, but human activities have enhanced this effect, leading to concerns about climate change.

The figures you mentioned, which show historical CO2 levels over hundreds of thousands of years and the sharp increase since 1750, illustrate the unprecedented rate of change. Historically, CO2 concentrations fluctuated naturally due to processes such as volcanic eruptions, ocean circulation, and biological activity. However, the current increase is largely attributed to anthropogenic (human-caused) factors:

1. Burning Fossil Fuels: The combustion of coal, oil, and natural gas for energy and transportation has released vast amounts of CO2 into the atmosphere. This is the primary source of increased atmospheric CO2 since the Industrial Revolution.

2. Deforestation: Forests act as carbon sinks, absorbing CO2 from the atmosphere. Deforestation for agriculture, urban development, and logging has reduced the number of trees, resulting in less CO2 absorption and additional CO2 emissions from the decay of organic matter and the burning of forest biomass.

The enhanced greenhouse effect leads to various climate-related challenges, including:

• Global Warming: Average global temperatures are rising, leading to more frequent and severe heatwaves, altered precipitation patterns, and rising sea levels.

• Ocean Acidification: Increased levels of CO2 are absorbed by oceans, causing a reduction in pH levels. This impacts marine life, particularly organisms with calcium carbonate shells, such as corals and some shellfish.

• Ecosystem Disruption: Changes in temperature and precipitation can alter habitats and biodiversity, leading to shifts in the distribution of species and potential extinctions.

• Extreme Weather Events: Climate change is linked to the increased frequency and intensity of extreme weather events, such as hurricanes, floods, and droughts.

Given these concerns, scientists and policymakers are engaged in efforts to mitigate the impacts of climate change through measures such as reducing greenhouse gas emissions, transitioning to renewable energy sources, promoting reforestation, and developing carbon capture technologies.

Understanding the relationship between human activities and atmospheric CO2 levels is crucial for predicting future climate scenarios and implementing effective strategies to address climate change. The information from Figures 1 and 2 provides vital context for these discussions and underscores the urgency of addressing the issue.